CN107540085A - It is a kind of to promote the anaerobism method that denitrification methane phase is efficiently carried out simultaneously - Google Patents

Abstract

The invention discloses a kind of method for promoting anaerobism simultaneous methanogenesis and denitrification efficiently to carry out.This method comprises the following steps：Anaerobic grain sludge is seeded in anaerobic reactor, it is passed through the waste water using sodium acetate and sodium propionate as mixed carbon source, using the nitrate nitrogen in waste water as nitrogen source, the influent COD of control waste water remains constant, gradually reduce C/N ratios, anaerobic reactor is run, promotes anaerobic waste water denitrification methane phase simultaneously.The inventive method is by controlling the ratio of carbon source kind and C/N, improve the reaction environment of anaerobism while denitrification methane phase, realize anaerobism while denitrification methane phase in single-reactor, reduce system adaptability time and hydraulic detention time simultaneously, contaminant removal efficiency height and stable effluent quality, and produce clean energy resource biogas.

Description

A method for promoting efficient anaerobic and simultaneous denitrification methane production

technical field

The invention belongs to the field of environmental protection, relates to anaerobic biological treatment of organic waste water, and in particular relates to a method for promoting the anaerobic denitrification of waste water and simultaneously denitrifying methane production with high efficiency.

Background technique

Among the current wastewater biological treatment methods, the anaerobic biological treatment method has been widely used due to its advantages such as high organic load tolerance, low energy consumption, low operating costs, small and stable residual sludge, and convenient management. A good treatment effect has been achieved.

In the anaerobic digestion process, it is divided into four stages: hydrolysis stage, acidification fermentation stage, acid production stage, and methane production stage. The hydrolysis stage is a biochemical process in which a compound is split into two or more simple compounds under the action of hydrolytic enzymes. In the acidification fermentation stage, the small molecule soluble compounds produced in the hydrolysis stage enter the cell interior of the acidifying bacteria through the cell membrane, transform into simpler end products such as volatile fatty acids, alcohols, lactose, etc., and secrete them outside the cell. The products of the acidogenic stage (the end of the acidification fermentation stage) are converted into acetic acid, CO ₂ , H ₂ and new cellular substances under the action of anaerobic microorganisms, oxygen-producing acetogens. The methanogenic stage is when methanogenic bacteria convert substances such as acetic acid, oxygen, carbonic acid, formic acid, and methanol into methane, carbon dioxide, and cellular matter.

In methanogenesis, methane formation is caused by a group of physiologically highly specialized archaea called methanogens. Methanogens are a special class of prokaryotic microorganisms that grow in a strictly anaerobic environment and are currently known to require the lowest redox potential. They cannot use complex organic matter as an energy source, but can only use hydrogen, carbon dioxide, formic acid, acetic acid and other simple substances to synthesize methane for energy metabolism, which is the last member of the anaerobic fermentation process. The biosynthesis of methane is the key to the carbon cycle in nature chain.

In the biological denitrification system, denitrifying bacteria can use carbon source as electron donor, NO ₃ ^- and NO ₂ ^- as electron acceptor, reduce NO ₃ ^- and NO ₂ ^- into nitrogen, and achieve the effect of removing organic matter at the same time. The denitrification reaction in the nitrogen-containing wastewater treatment process is that NO ₃ ^- -N is converted into nitrogen gas and N ₂ escapes from the water under the action of denitrifying bacteria. In addition to the denitrification of nitrogen, the conversion of nitrogen by microorganisms in this system may also have dissimilatory nitrate reduction to ammonium (DNRA). At the same time, the type of carbon source in the influent is also an important factor affecting the effect of biological nitrogen removal.

It is generally considered that methanogens and denitrifiers are two types of microorganisms with very different properties. In an anaerobic simultaneous denitrification methanogenic system, different COD/NO _x ^- -N ratios and different carbon sources will affect the metabolism of substrates such as carbon and nitrogen. Different microorganisms in the system inhibit and compete for substrate substrates, thus forming different population structures under specific conditions.

Studies have shown that denitrifying bacteria and methanogenic bacteria have very different requirements for the living environment, and nitrogen-containing compounds have competitive and toxic inhibitory effects on the methanogenic reaction. Among them, the intermediate products (nitrogen oxides) in the denitrification process of denitrifying bacteria have a certain poisonous effect on methanogens, thus hindering the decarbonization process. In addition, the operation of the reactor also showed that the strength of the granular sludge produced by simultaneous methane denitrification was smaller than that produced by methanation alone, and even the sludge disintegrated due to the increase of nitrate nitrogen load.

Contents of the invention

The purpose of the present invention is to provide a method for promoting efficient anaerobic simultaneous denitrification and methane production in order to solve the shortcomings of single reactor anaerobic simultaneous denitrification and methane production in the prior art, including long residence time and removal efficiency . The method controls the type of carbon source and the ratio of C/N, thereby promoting the anaerobic and simultaneous denitrification of wastewater to produce methane, and efficiently treating the organic wastewater containing carbon and nitrogen.

The purpose of the present invention is achieved through the following technical solutions.

A method for promoting anaerobic simultaneous denitrification to produce methane efficiently, comprising the following steps:

Inoculate the anaerobic granular sludge in the anaerobic reactor, feed the wastewater with sodium acetate and sodium propionate as the mixed carbon source, and use the nitrate nitrogen (NO ₃ ^- -N) in the wastewater as the nitrogen source to run the anaerobic reactor. The reactor controls the influent COD of the wastewater to remain constant, gradually reduces the C/N ratio, and promotes the anaerobic denitrification of the wastewater while producing methane.

Further, the anaerobic granular sludge is taken from a well-run anaerobic reactor, and the VSS/TSS (volatile suspended solids/total suspended solids) is not less than 50%.

Further, the anaerobic reactors used are widely used anaerobic reactors, including IC reactors, which can ensure a complete anaerobic environment inside the reactor during operation.

The IC reactor is selected as the anaerobic simultaneous denitrification methane reactor, which has the advantages of high machine load, time saving, low energy consumption, low operating cost, small and stable residual sludge, and stable effluent quality.

Further, the ratio of sodium acetate to sodium propionate is 1:1.

Further, during operation, the influent COD of the wastewater does not exceed 3000mg/L.

Further, trace elements of 0.1% of the waste water mass are added to the waste water.

Further, during the operation, the temperature of the feed water and the temperature in the reactor is controlled at 31-37°C.

Further, the pH value of the influent is controlled to not be lower than 7.2, and the pH buffering capacity of the system is maintained by adding bicarbonate in the influent to maintain the pH value of the system not lower than 7.2.

Further, during the operation, the hydraulic retention time is 20~28h.

Further, the C/N ratio is finally stable at 10:1.

Further, the process of gradually reducing the C/N ratio is as follows: on the 0th-10th day, control the concentration of nitrate nitrogen in the influent to 0 mg/L; on the 11th-20th day, control the C/N ratio in the influent to 40 :1, the highest concentration of nitrate nitrogen in the influent is 75mg/L; on the 21st-30th day, the ratio of C/N in the control influent is 20:1, and the highest concentration of nitrate nitrogen in the influent is 150mg/L; On the 31st-40th day, the C/N ratio of the influent is controlled to be 10:1, and the maximum concentration of nitrate nitrogen in the influent is 300mg/L.

The C/N ratio is finally stable at 10:1, which ensures that the C/N ratio can be operated at 40~10:1.

In the process of anaerobic and simultaneous denitrification of wastewater to produce methane, the wastewater first enters the water distribution system at the bottom of the reactor through the peristaltic pump, fully mixes with the mud-water mixture from the downcomer, and then enters the granular sewage in the first reaction chamber. The mud expanded bed carries out biodegradation of COD and NO ₃ ^- -N, most of the organic matter in the wastewater is degraded here, and a large amount of biogas is generated; the generated biogas is lifted along the biogas together with the mud-water mixture in the first reaction chamber The pipe rises to the gas-liquid separator at the top, most of the biogas is separated from the mixed liquid and discharged from the pipe of the separator, and the mud-water mixed liquid returns to the bottom of the reactor along the return pipe due to gravity, and is mixed with the influent water and the granular sludge at the bottom Mix well to create an inner loop. Due to the formation of internal circulation, the first reaction chamber not only has a higher biomass, but also has a larger liquid-phase ascending flow rate, so that the granular sludge in the first reaction chamber is in a fluidized state. The effluent from the first reaction chamber automatically enters the second reaction chamber for further processing, the remaining organic matter in the wastewater is further biodegraded, and the generated biogas is collected by the gas collection hood of the second reactor and rises to the gas-liquid at the top along the riser The separator performs separation and is collected after being discharged from the exhaust port.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

The method of the present invention improves the reaction environment of anaerobic simultaneous denitrification and methane production by controlling the type of carbon source and the ratio of C/N, realizes anaerobic simultaneous denitrification and methane production in a single reactor, and simultaneously reduces the system adaptability time and hydraulic retention time, the pollutant removal efficiency is high, the effluent water quality is stable, and clean energy biogas is generated.

Description of drawings

Fig. 1 is the COD concentration of effluent and the COD removal rate change graph with time in embodiment 1;

Fig. 2 is a graph showing the concentration of nitrate nitrogen (NO ₃ ^- -N) in the influent and effluent water and its removal rate over time in Example 1.

detailed description

The technical solutions of the present invention will be described in further detail below in conjunction with specific implementation methods and accompanying drawings, but the protection scope of the present invention is not limited thereto.

In a specific embodiment of the present invention, the method for promoting anaerobic simultaneous methanogenic denitrification to be carried out efficiently comprises the following steps:

The anaerobic granular sludge taken from the bottom of a well-run IC reactor in a wastewater treatment plant was used as inoculation sludge, which was inoculated in the IC reactor. Suspended solids (VSS) concentration is 20.35g/L, VSS/SS=69.19%;

Feed wastewater with sodium propionate and sodium acetate (molar ratio 1:1) as a mixed carbon source, the influent COD is 3000mg/L, and NaNO ₃ in wastewater is used as nitrogen source, and the COD concentration in wastewater is maintained at 3000mg/L L remains unchanged, the NO ₃ ^- -N content is gradually increased to gradually reduce the C/N ratio, and finally the NO ₃ ^- -N content is stabilized at 300mg/L, and the C/N ratio is maintained at 10:1 for anaerobic simultaneous reaction. Nitrification methanogenesis reaction, the specific process is: first, on the 0th to 10th day, control the concentration of NO ₃ ^- -N in the influent to 0 mg/L; on the 11th to 20th day, control the C/N in the influent to 40: 1. The concentration of NO ₃ ^- -N is 75mg/L; on the 21st-30th day, the C/N ratio in the influent water is controlled to be 20:1, and the concentration of NO ₃ ^- -N is 150mg/L; on the 31st-40th day , control the influent C/N to be 10:1, and the concentration of NO ₃ ^- -N to be 300mg/L;

At the same time, trace elements of 0.1% of the wastewater quality are added to the wastewater. During the operation, the temperature of the influent water and the reactor is kept at 35±1°C through the heating device, the hydraulic retention time is 24h, and bicarbonate is added to adjust the reaction system. The pH value is 7.6±0.2.

Example 1

The method for promoting the efficient production of methane by anaerobic simultaneous denitrification comprises the following steps:

(1) The anaerobic granular sludge taken from the bottom of the well-run IC reactor in the wastewater treatment plant was used as the inoculation sludge, which was inoculated in the IC reactor. The total suspended solids (TSS) concentration of the sludge at the time of inoculation was 29.41g/L , the concentration of volatile suspended solids (VSS) is 20.35g/L, VSS/TSS=69.19%, and the inoculation amount of anaerobic granular sludge is 1L;

Use artificially prepared wastewater with sodium propionate and sodium acetate (sodium propionate: sodium acetate = 1:1, molar ratio) as a mixed carbon source, the COD of the wastewater is 3000mg/ _L , and the wastewater uses NaNO3 as the nitrogen source;

By adding bicarbonate to ensure that the pH value of the wastewater is stable between 7.6±0.2; at the same time, trace elements are added to the influent water. The composition and ratio of trace elements are: EDTA 5.0 g/L, CaCl ₂ 2H ₂ O 5.5g/ L, FeSO ₄ 7H ₂ O 5.0g/L, ZnSO4 7H ₂ O 2.2g/L, CoCl ₂ 6H ₂ O 1.6g/L, MnCl ₂ 6H ₂ O 5.0g/L, CuSO ₄ 5H ₂ O 5.0g/L, MgSO ₄ 7H ₂ O 1.6g/L, NiCl ₂ 6H ₂ O 0.6g/L, Na ₂ MoO ₄ 2H ₂ O 5.0g/L;

During the operation of the IC reactor, the temperature of the inlet water and the reactor is kept at 35±1°C through the heating device, and the hydraulic retention time of the wastewater is 24h;

By adjusting the ratio of m(COD)/m(NO ₃ ^- -N), the waste water was subjected to anaerobic and simultaneous denitrification methanogenesis reaction in the IC reactor, and the influent COD concentration of the waste water was kept at 3000 mg/L, and the NO ₃ ^- The -N content is gradually increased and finally the NO ₃ ^- -N content is stabilized at 300mg/L, and the C/N ratio is maintained at 10:1 to carry out anaerobic and simultaneous denitrification methane reaction. The specific process is as follows: first at the 0-10 day, the concentration of NO ₃ ^- -N in the control influent was 0mg/L; on the 11th-20th day, the C/N in the control influent was 40:1, and the concentration of NO ₃ ^- -N was 75mg/L; On the 21st-30th day, control the C/N ratio of the influent to 20:1, and the concentration of NO ₃ ^- -N to 150mg/L; on the 31st-40th day, control the influent C/N to 10:1, NO The concentration of ₃ ^- -N is 300mg/L.

The COD concentration and COD removal rate of the effluent change with time is shown in Figure 1. It can be seen from Figure 1 that when the COD of the influent is maintained at about 3000, the COD of the effluent in the first stage (0-10 days) The removal rate reached 85.53%; after adding NO ₃ ^- -N in the second stage (day 11-20), the removal rate of COD in the effluent increased to 91.59%; The removal rate continued to rise, reaching 94.98%; in the fourth stage (31-40 days), the removal rate of COD in the effluent was stable above 96%.

The concentration of nitrate nitrogen (NO ₃ ^- -N) in the influent and effluent water and its removal rate over time are shown in Figure 2. It can be seen from Figure 2 that no NO ₃ ^- -N was added in the first stage (0-10 days). , to adapt the anaerobic granular sludge to the wastewater environment; after the removal rate of NO ₃ ^- -N in the effluent was stabilized at 97% in the second stage (day 11-20), the concentration of NO ₃ ^- -N in the influent was further increased; In the third stage (day 21-30), the concentration of NO ₃ ^- -N in the effluent was 4.11 mg/L, and the removal rate of NO ₃ ^- -N reached 97.26%; in the fourth stage (day 31-40), the NO ₃ ^- -N The concentration of -N in the influent water increased further, and the removal rate of NO ₃ ^- -N in the effluent water remained at 97%. Combining with Figure 1, it can be seen that the removal rate of COD in the water was stable above 96%.

The above results show that when the IC reactor is used to treat wastewater with a mixed carbon source of sodium acetate and sodium propionate and nitrate as a nitrogen source, the carbon source COD concentration is maintained at 3000 mg/L, and the influent NO ₃ ^- -N concentration, by controlling the C/N ratio to gradually increase, the efficient progress of anaerobic simultaneous denitrification and methane production in a single reactor is realized, so that the removal rate of effluent COD is stable above 96% and effluent NO ₃ ^- - The removal rate of N reaches 97% stably, and the removal rate of organic pollutants in the effluent is high; at the same time, the quality of the effluent is stable and reduces the short adaptability time of the reaction system and the hydraulic retention time

The above examples are only preferred implementations of the present invention, and are only used to explain the present invention, rather than limit the present invention. Changes, replacements, modifications, etc. made by those skilled in the art without departing from the spirit of the present invention shall belong to the present invention. protection scope of the invention.

Claims (10)

1. A method for promoting anaerobic simultaneous denitrification to produce methane efficiently, is characterized in that, comprises the steps: Inoculate the anaerobic granular sludge in the anaerobic reactor, feed the wastewater with sodium acetate and sodium propionate as the mixed carbon source, and use the nitrate nitrogen in the wastewater as the nitrogen source to run the anaerobic reactor to control the inflow of wastewater. Water COD remains unchanged, and the C/N ratio is gradually reduced to promote anaerobic and simultaneous denitrification of wastewater to produce methane. 2. The method according to claim 1, wherein the VSS/TSS of the anaerobic granular sludge is not less than 50%. 3. method according to claim 1, is characterized in that, the mol ratio of described sodium acetate and sodium propionate is 1:1. 4. The method according to claim 1, characterized in that, during operation, the influent COD of the wastewater does not exceed 3000mg/L. 5. The method according to claim 1, characterized in that, the trace element of waste water quality 0.1% is added in the waste water. 6. The method according to claim 1, characterized in that, during the operation, the water temperature of the feed water is controlled and the temperature in the reactor is kept at 31-37°C. 7. The method according to claim 1, characterized in that, during operation, the pH value of the influent water is controlled to be not lower than 7.2. 8. The method according to claim 1, characterized in that, during operation, the hydraulic retention time is 20 to 28 hours. 9. The method according to claim 1, wherein the C/N ratio is finally stabilized at 10:1. 10. The method according to claim 1, characterized in that, the process of gradually reducing the C/N ratio is as follows: on the 0th-10th day, control the concentration of nitrate nitrogen in the influent to 0 mg/L; on the 11th-20th day day, control the C/N ratio in the influent to 40:1, and the maximum concentration of nitrate nitrogen in the influent is 75 mg/L; on the 21st to 30th day, control the influent C/N ratio to 20:1, The maximum concentration of nitrate nitrogen is 150mg/L; on the 31st-40th day, the C/N ratio of the influent is controlled to be 10:1, and the maximum concentration of nitrate nitrogen in the influent is 300mg/L.